The present invention relates generally to gasification plants, and more particularly, to methods and apparatus for optimizing synthetic gas production with a gasification system via acid gas removal.
At least some known gasification plants include a gasification system that is integrated with at least one power-producing turbine system, thereby forming an integrated gasification combined cycle (IGCC) power generation plant. For example, known gasification systems convert a mixture of fuel, air or oxygen, steam, and/or CO2 into a synthetic gas, or “syngas”. The syngas is channeled to the combustor of a gas turbine engine, which powers a generator that supplies electrical power to a power grid. Exhaust from at least some known gas turbine engines is supplied to a heat recovery steam generator (HRSG) that generates steam for driving a steam turbine. Power generated by the steam turbine also drives an electrical generator that provides electrical power to the power grid.
At least some known gasification systems associated with IGCC plants initially produce a “raw” syngas fuel which includes carbon monoxide (CO), hydrogen (H2), carbon dioxide (CO2), carbonyl sulfide (COS), and hydrogen sulfide (H2S). CO2, COS, and H2S are typically referred to as acid gases. Acid gas is generally removed from the raw syngas fuel to produce a “clean” syngas fuel for combustion within the gas turbine engines. Such acid gas removal is performed with an acid gas removal subsystem that typically includes at least one main absorber to remove a majority of H2S and COS. Such acid gas removal subsystems also typically include at least one ancillary absorber that “scrubs” predetermined components from associated fluid streams to predetermined values. Many known absorbers are positioned between acid gas removal subsystem conduits and conduits that permit scrubbed gas streams to be released to the environment. These ancillary absorbers are normally in service only during predetermined operational activities, for example, plant startups and component failure-related transients. The typical number of absorbers used increases the number and length of associated piping runs and the number of absorber vessels that are provided, installed and operated, thereby increasing the overall cost of ownership of the IGCC plant with little additional cost-effective duty realized. Moreover, most known ancillary absorbers do not facilitate decreasing the concentration of H2S and COS within the associated gas streams.